Acute Rheumatic Fever: Penicillin Prophylaxis
This 3-year-old with migratory arthritis (left knee resolving as right knee becomes involved) has acute rheumatic fever (ARF) following group A streptococcal infection, and requires penicillin treatment for 10 days followed by long-term secondary prophylaxis—the answer is A (Penicillin 10 days). 1
Clinical Presentation Confirms ARF
The migratory pattern of arthritis—where one joint improves as another becomes inflamed—is pathognomonic for acute rheumatic fever rather than septic arthritis or juvenile idiopathic arthritis. 1
- Migratory polyarthritis is the hallmark feature distinguishing ARF from other pediatric arthritides, with joints becoming inflamed sequentially while previously affected joints resolve 1
- This occurs as a non-suppurative autoimmune complication following group A streptococcal pharyngitis, typically 2-4 weeks after the initial infection 1
- In children under 4 years, while Kingella kingae is a common cause of septic arthritis, the migratory pattern rules this out 2, 3
Treatment Protocol
Acute Phase Treatment
- Penicillin for 10 days is the first-line therapy to eradicate any residual group A streptococcal infection 4
- Penicillin remains exquisitely sensitive to group A streptococcus and is recommended by the American Academy of Pediatrics and American Heart Association 4
- The 10-day duration is necessary to optimize bacterial eradication and prevent rheumatic fever complications 4
Secondary Prophylaxis (Critical)
- Long-term penicillin prophylaxis is mandatory after the initial 10-day treatment course to prevent recurrent ARF and subsequent rheumatic heart disease 1
- This distinguishes ARF management from post-streptococcal reactive arthritis, where secondary prophylaxis is not required 1
- Monthly intramuscular benzathine penicillin G is the standard regimen for secondary prophylaxis, though this is separate from the initial 10-day treatment 4
Why Other Options Are Incorrect
Streptococcus vaccine (Option B): No vaccine exists for group A streptococcus 4
Monthly prophylaxis (Option C): While monthly benzathine penicillin is used for secondary prophylaxis after ARF diagnosis, the initial treatment requires a 10-day course first 4
Aspirin (Option D): Aspirin provides symptomatic relief for arthritis but does not address the underlying streptococcal infection or prevent cardiac complications 1
Critical Pitfall to Avoid
The most dangerous error would be treating this as septic arthritis with surgical drainage, as the migratory pattern definitively excludes bacterial joint infection. 2 Septic arthritis presents with persistent monoarticular involvement and requires arthrocentesis, whereas ARF demonstrates sequential joint involvement with spontaneous resolution of previously affected joints. 2, 1